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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 32, Number 8
BKCSDE 32(8)
August 20, 2011 

Phase Transition of Octaneselenolate Self-assembled Monolayers on Au(111) Studied by Scanning Tunneling Microscopy
Jungseok Choi, Hungu Kang, Eisuke Ito, Masahiko Hara, Jaegeun Noh*
Octaneselnolate, Self-assembled monolayers, Scanning tunneling microscopy, Phase transition, Contact angle
We investigated the surface structure and wetting behavior of octaneselenolate self-assembled monolayers (SAMs) on Au(111) formed in a 50 μM ethanol solution according to immersion time, using scanning tunneling microscopy (STM) and an automatic contact angle (CA) goniometer. Closely-packed, well-ordered alkanethiol SAMs would form as the immersion time increased; unexpectedly, however, we observed the structural transition of octaneselenolate SAMs from a molecular row phase with a long-range order to a disordered phase with a high density of vacancy islands (VIs). Molecularly resolved STM imaging revealed that the missing-row ordered phase of the SAMs could be assigned as a (6 × √3)R30° superlattice containing three molecules in the rectangular unit cell. In addition, CA measurements showed that the structural order and defect density of VIs are closely related to the wetting behaviors of octaneselenolate SAMs on gold. In this study, we clearly demonstrate that interactions between the headgroups and gold surfaces play an important role in determining the physical properties and surface structure of SAMs.
2623 - 2627
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